阅读说明：本技术 一种双官能团的化合物、其合成方法及作为抗氧剂的应用 (bifunctional compounds, synthesis method thereof and application thereof as antioxidant ) 是由 李广全 段宏义 李丽 吴建 杨喜棠 高杜娟 刘芸 赵东波 杨世元 熊华伟 杨柳 于 2018-07-20 设计创作，主要内容包括：一种双官能团的化合物、其合成方法及作为抗氧剂的应用,该双官能团的化合物是由受阻酚单元、亚磷酸酯单元、三甲基苯单元和直链链段单元共同构成。通过控制直链链段单元的长度调整受阻酚单元和亚磷酸酯单元的协同作用强弱和单位质量里有效的官能团的含量,三甲基苯结构有利于防止抗氧剂化合物从聚合物中的析出。本发明化合物可作为聚丙烯或聚乙烯的抗氧化剂使用。(bifunctional compounds, its synthesis method and its application as antioxidant, the bifunctional compounds are composed of hindered phenol unit, phosphite unit, trimethylbenzene unit and straight chain segment unit, the length of straight chain segment unit is controlled to adjust the synergistic action strength of hindered phenol unit and phosphite unit and the content of effective functional group in unit mass, the trimethylbenzene structure is favorable to prevent the antioxidant compound from separating out from the polymer.)

1, bifunctional compounds characterized by the structural formula:

wherein n is a positive integer from 3 to 16.

A method of synthesizing the compound of claim 1, comprising the steps of:

step 1, etherification of 2, 6-di-tert-butylphenol: adding 2, 6-di-tert-butylphenol and paraformaldehyde into a reactor, and mixing the components in a molar ratio: 2, 6-di-tert-butylphenol: 1, 1.5-2.0 parts of paraformaldehyde, simultaneously adding a reaction solvent, reacting at 100-150 ℃ for 2-5 h under the catalytic action of 0.1-1.0 ml of piperazine and ethylenediamine, cooling the reaction solution to room temperature after the reaction is completed, filtering, washing and drying to obtain pure 3, 5-di-tert-butyl-4-hydroxybenzyl methyl ether;

step 2, condensation reaction: adding 3, 5-di-tert-butyl-4-hydroxybenzyl methyl ether and mesitylene into a reactor according to the mol ratio of 3, 5-di-tert-butyl-4-hydroxybenzyl methyl ether: 3-4: 1 of mesitylene, adding a reaction solvent, controlling the reaction temperature at-20-0 ℃, adding concentrated sulfuric acid into the reaction solution, keeping the molar ratio of the concentrated sulfuric acid to the mesitylene at 1: 2-4, continuously stirring for 0.5-1 h, standing the reaction solution, collecting the upper layer liquid, adding water, ammonia water and the upper layer liquid obtained by the reaction into a reactor, heating, stirring and heating to 70-90 ℃, then adding n-heptane, heating to reflux, cooling, separating, washing the supernatant until the pH value is 5-8, cooling the washed supernatant to 40-50 ℃ in air, cooling to 0-10 ℃, standing for 0.5-1 h, filtering, washing the solid with n-heptane, drying at 40-50 ℃ to obtain white crystals, namely the product 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene;

and 3, protecting phenolic hydroxyl: 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene: adding dimethyl sulfate (1: 1.1-2) into a reactor, adding a reaction solvent, reacting at 45-61 ℃ for 0.1-2 h under the protection of nitrogen, cooling the reaction solution to room temperature after the reaction is completed, adding a diluted potassium carbonate solution into the reaction solution, extracting, drying an organic phase, and evaporating to dryness to obtain pure 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-methoxybenzyl) benzene;

step 4, mono α bromination of 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-methoxybenzyl) benzene, namely adding N-bromosuccinimide into a reactor according to a molar ratio of 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-methoxybenzyl) benzene to 3-4: 1, adding a reaction solvent at the same time, dropwise adding the N-bromosuccinimide into a reaction solution under the catalysis of azodiisobutyronitrile under the protection of nitrogen, stirring and heating to 50-77 ℃, and reacting for 2-5 hours to generate 1-bromomethyl-3, 5-dimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-methoxybenzyl) benzene;

and step 5, carrying out alcoholization reaction on 1-bromomethyl-3, 5-dimethyl-2, 4, 6-tri (3, 5-di-tert-butyl-4-methoxybenzyl) benzene: the molar ratio of 1-bromomethyl-3, 5-dimethyl-2, 4, 6-tri (3, 5-di-tert-butyl-4-methoxybenzyl) benzene: adding a diol compound which is 1: 1.1-2 into a reactor, adding an alkaline substance in an equimolar amount with 1-bromomethyl-3, 5-dimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-methoxybenzyl) benzene, simultaneously adding a reaction solvent, heating the reaction solution to reflux, and reacting for 5-60 hours to generate diol mono- [3, 5-dimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-methoxybenzyl) ] anisole;

step 6, preparing phosphite ester, namely adding the diol mono- [3, 5-dimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-methoxybenzyl) ] anisole prepared by the reaction in the previous step into a reactor, simultaneously adding a reaction solvent, controlling the reaction liquid to be 0-20 ℃ under the protection of nitrogen, dropwise adding phosphorus trichloride of which the molar weight is - half of the third of the alcohol substance into the reaction liquid for 0.5-5 hours, heating the reaction liquid to 130-135 ℃ after dropwise adding is finished and the temperature is kept for continuous reaction for 2-10 hours, and refluxing for 2-5 hours under negative pressure to obtain the phosphite ester compound;

and 7, deprotection reaction of hydroxyl: and (3) mixing the phosphite ester compound obtained in the step 6 and boron tribromide in a molar ratio of phosphite ester: adding boron tribromide in a ratio of 1: 1-3 into a reactor, adding a reaction solvent, cooling the temperature of the reaction solution to 0-50 ℃, dropwise adding a dichloromethane solution in which boron tribromide is dissolved in advance at a concentration of 10-100 g/L into the reaction solution for 1-5 h, returning the reaction solution to room temperature after dropwise adding, and stirring for 2-5 h.

3. The process of claim 2 wherein in step 5 the basic catalyst is sodium hydroxide, potassium carbonate or sodium carbonate.

4. The method according to claim 2, wherein the number of carbon atoms of the diol compound in the step 5 is a positive integer of 3 to 16.

5. The method of claim 2, wherein the solvent added in step 1 is selected from of methanol, ethanol, chloroform and toluene.

6. The method of claim 2, wherein the solvent added in step 2 is selected from of benzene, dichloromethane, chloroform and carbon tetrachloride.

7. The method of claim 2, wherein the solvent added in step 3 is selected from kinds of chlorobenzene, dichloromethane, chloroform and toluene.

8. The method of claim 2, wherein the solvent added in step 4 is selected from of benzene, dichloromethane, chloroform and carbon tetrachloride.

9. The method of claim 2, wherein the solvent added in step 5 is selected from of methanol, ethanol, acetone, and dimethylformamide.

10. The method of claim 2, wherein the solvent added in step 6 is selected from kinds of triethylamine, ethanol, dimethylformamide, toluene, xylene, benzene, chlorobenzene, dichloromethane, carbon tetrachloride and ethyl acetate.

11. The method of claim 2, wherein the solvent added in step 7 is selected from of dichloromethane, chloroform and carbon tetrachloride.

Use of compounds according to claim 1, characterized in that said compounds are used as antioxidants for polyolefin resins.

13. The use according to claim 12, wherein the compound is added to the polyolefin resin base in a mass percentage of 0.01% to 1%.

Technical Field

The invention relates to compounds and a synthesis method thereof, in particular to a compound containing both hindered phenol and phosphite bifunctional in single molecules and a synthesis method thereof, wherein the compound can be used as an antioxidant of polyolefin.

Background

Hindered phenolic compounds compete with polymers for peroxy radicals formed in autoxidation, and through transfer of hydrogen atoms, carboxylic acids and stable antioxidant radicals are formed, which have the ability to capture active radicals and can terminate the second kinetic chain of polymer chain oxidation reaction, phosphite compounds decompose peroxides into stable products through conversion from the phosphite compounds themselves into phosphate compounds to protect the polymers, the hindered phenolic compounds and phosphite compounds show a very good synergistic effect in the antioxidation aspect of the polymers, for example, after antioxidant 1010, 1076 and 168 produced by gasoline refining are compounded, is used in antioxidants of products such as polyolefin, ABS resin, synthetic rubber and polyester.

Hindered phenolic antioxidants are generally produced by transesterification under basic conditions. Such as: US4716244, US5481023, US5563291, US6878843, US2003166962, WO198249 describe the preparation of hindered phenolic antioxidants (e.g. antioxidants 1010, 1076, 245 and 1135) using lithium amide, lithium acetate, sodium acetate, magnesium acetate, aluminum triethoxide, zinc acetate, etc. as catalysts. Phosphite antioxidants are generally prepared by reacting alcohol compounds with phosphorus trichloride. Such as: CN200510112503.9, cn200710056079.x, cn200710176407.x describe the process of obtaining phosphite antioxidants by ester exchange of pentaerythritol or nonylphenol with phosphorus trichloride in a solvent.

Meanwhile, when the antioxidant effect is increased by utilizing the mutual synergistic effect of the hindered phenol antioxidant and the phosphite antioxidant, the distance of the two molecules after dispersion in the resin or the rubber is difficult to control, so that the synergistic effect can be influenced, CN103319523A describes bifunctional antioxidants containing both hindered phenol and phosphite structures in the same molecules, and the antioxidant effect is improved by utilizing the synergistic effect of the hindered phenol antioxidant and the phosphite.

At present, medical infusion bottles and containers in direct contact with food in China are manufactured by adopting special polypropylene or polyethylene resin, the polypropylene or polyethylene material is aged by the action of heat, light, an electric field, rays, metal ions or chemical media and the like in the processes of forming, storing and using, and an antioxidant is required to be added in production, at present, hindered phenol antioxidants and phosphite antioxidants are respectively added into the polypropylene, the adding amount is more than 0.1%, European pharmacopoeia stipulates that the content of a single antioxidant does not exceed 0.3%, and the total amount does not exceed 0.3%.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide antioxidant compounds which have excellent performance, contain bifunctional groups and are resistant to precipitation and a synthesis method thereof.

The structure of the compound provided by the invention is as follows:

wherein n is a positive integer from 3 to 16;

the purpose of the invention can be realized by the following technical scheme:

A process for synthesizing the bifunctional antioxidizing agent includes such steps as 2, 6-di-tert-butylphenol, paraformaldehyde, piperazine, ethanediamine, mesitylene, dimethyl sulfate, N-bromosuccinimide, azodiisobutyronitrile, straight-chain diol, phosphorus trichloride, and boron tribromide solution.

Step 1, etherification of 2, 6-di-tert-butylphenol

Adding 2, 6-di-tert-butylphenol and paraformaldehyde into a reactor, and mixing the components in a molar ratio:

2, 6-di-tert-butylphenol: formaldehyde 1: 1.5-2.0

Simultaneously adding a reaction solvent, wherein the reaction solvent is at least selected from methanol, ethanol, chloroform and toluene;

under the catalytic action of a small amount of piperazine and ethylenediamine, the reaction temperature is 100-150 ℃, the reaction time is 2-5 h, and 3, 5-di-tert-butyl-4-hydroxybenzyl methyl ether is generated;

according to a theoretical value, the mole number of the polyformaldehyde and the 2, 6-di-tert-butylphenol is equal, and in practical application, the added polyformaldehyde needs to be obviously excessive so as to ensure the complete reaction of the 2, 6-di-tert-butylphenol. After the reaction is completed, cooling the reaction liquid to room temperature, filtering, washing and drying to obtain pure 3, 5-di-tert-butyl-4-hydroxybenzyl methyl ether.

Step 2, condensation reaction

Adding 3, 5-di-tert-butyl-4-hydroxybenzyl methyl ether and mesitylene into a reactor according to the mol ratio:

3, 5-di-tert-butyl-4-hydroxybenzyl methyl ether: 3-4: 1 of mesitylene

Simultaneously adding a reaction solvent, wherein the reaction solvent is at least selected from dichloromethane, chloroform, chlorobenzene and carbon tetrachloride;

controlling the reaction temperature to be-20-0 ℃ by adopting an ice salt bath, and slowly dripping concentrated sulfuric acid with the mass concentration of 0.8-0.9% into the reaction solution, wherein the molar ratio of the concentrated sulfuric acid to mesitylene is 1: 2-4. And after the dropwise addition is finished, continuously stirring for 0.5-1 h, pouring the reaction liquid into a separating funnel, standing and collecting the upper layer liquid.

Deionized water, ammonia water and the supernatant liquid obtained by the above reaction were added to a reactor equipped with a stirrer, a thermometer and a condenser. Heating, stirring and heating to 70-90 ℃, and then adding n-heptane and heating to reflux. And cooling to room temperature, and washing the supernatant with deionized water after settling separation until the pH value is 5-8. And cooling the washed clear liquid to 40-50 ℃ in air, cooling the clear liquid to 0-10 ℃ by using an ice water bath, standing the clear liquid for 0.5-1 h, filtering the clear liquid, washing the solid by using n-heptane, and drying the solid at the temperature of 40-50 ℃ to obtain white crystals, namely the product 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene.

According to a theoretical value, the ratio of the 3, 5-di-tert-butyl-4-hydroxybenzyl methyl ether to the mesitylene is 3:1, and in practical application, a slight excess of the 3, 5-di-tert-butyl-4-hydroxybenzyl methyl ether is added to ensure that three 3, 5-di-tert-butyl-4-hydroxybenzyl methyl ether groups are simultaneously connected to the mesitylene in the condensation reaction process.

And 3, protecting phenolic hydroxyl:

adding 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene and dimethyl sulfate into a reactor according to the mol ratio:

1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene: 1: 1.1-2 dimethyl sulfate

Simultaneously adding a reaction solvent, wherein the reaction solvent is at least selected from chlorobenzene, dichloromethane, chloroform and toluene;

under the protection of nitrogen, the reaction temperature is 45-61 ℃, the reaction time is 0.1-2 h, and 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-methoxybenzyl) benzene is generated;

the phenolic hydroxyl protection reaction process is as follows:

in the process of phenolic hydroxyl protection reaction, hydrogen spectrum of nuclear magnetic resonance is used¹H NMR analysis monitored the 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene content in the reaction until no 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene was detected in the reaction, typically times every 10 minutes, or with unequal intervals.

According to a theoretical value, the dimethyl sulfate is half of that of 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene, and in practical application, the added dimethyl sulfate is obviously excessive to ensure the complete reaction of the 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene.

And cooling the reaction liquid to room temperature after the reaction is completed, adding a diluted potassium carbonate solution into the reaction liquid for extraction, drying an organic phase, and evaporating to dryness to obtain pure 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-methoxybenzyl) benzene.

Step 4, mono α bromination of 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-methoxybenzyl) benzene:

adding 1,3, 5-trimethyl-2, 4, 6-tri (3, 5-di-tert-butyl-4-methoxybenzyl) benzene and N-bromosuccinimide into a reactor according to the mol ratio,

1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-methoxybenzyl) benzene: 3-4: 1 of N-bromosuccinimide

Simultaneously adding a reaction solvent, wherein the reaction solvent is at least selected from benzene, dichloromethane, chloroform and carbon tetrachloride;

under the protection of nitrogen, under the catalytic action of azodiisobutyronitrile, slowly dropwise adding N-bromosuccinimide into the reaction solution at low temperature, continuously stirring after dropwise adding is finished, raising the temperature of the reaction to 50-77 ℃ and reacting for 2-5 hours to generate 1-bromomethyl-3, 5-dimethyl-2, 4, 6-tri (3, 5-di-tert-butyl-4-methoxybenzyl) benzene.

The equation for the bromination reaction is:

and in the bromination reaction process, observing the color of the reaction solution, and continuing to react for 1-2 hours after the orange color of the reaction solution disappears and white precipitate is generated.

The intermediate product 1-bromomethyl-3, 5-dimethyl-2, 4, 6-tri (3, 5-di-tert-butyl-4-methoxybenzyl) benzene can be purified by a column chromatography method, a developing agent is a mixed solution of dichloromethane and methanol, and after unreacted 1,3, 5-trimethyl-2, 4, 6-tri (3, 5-di-tert-butyl-4-methoxybenzyl) benzene is collected by column chromatography, mono α bromination reaction can be carried out again.

Step 5, alcoholization reaction of 1-bromomethyl-3, 5-dimethyl-2, 4, 6-tri (3, 5-di-tert-butyl-4-methoxybenzyl) benzene

Adding 1-bromomethyl-3, 5-dimethyl-2, 4, 6-tri (3, 5-di-tert-butyl-4-methoxybenzyl) benzene and diol compounds into a reactor according to a molar ratio,

1-bromomethyl-3, 5-dimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-methoxybenzyl) benzene: a diol compound of 1:1.1 to 2

Adding an alkaline substance with the same molar weight as 1-bromomethyl-3, 5-dimethyl-2, 4, 6-tri (3, 5-di-tert-butyl-4-methoxybenzyl) benzene to obtain an alkaline catalyst, wherein the alkaline catalyst can be: sodium hydroxide, potassium carbonate and sodium carbonate.

Simultaneously adding a reaction solvent, wherein the reaction solvent is at least selected from methanol, ethanol, acetone and dimethylformamide;

under the catalytic action of alkaline substances, the reaction liquid is heated to reflux, and the reaction time is 5 to 60 hours, so that the glycol mono- [3, 5-dimethyl-2, 4, 6-tri (3, 5-di-tert-butyl-4-methoxybenzyl) ] anisole is generated.

The equation for the bromination reaction is:

diol HO (CH) used in the reaction₂) n in nOH is an integer of 3-16.

During the reaction, different displacement values of the thin-layer chromatography of the reactants and the product on a silica gel plate are utilized, chloroform and methanol are used as developing agents, the gradual lightening of the color point of 1-bromomethyl-3, 5-dimethyl-2, 4, 6-tri (3, 5-di-tert-butyl-4-methoxybenzyl) benzene is monitored until the color point is not changed any more, the heating is stopped, the reaction liquid is recovered to the room temperature, then distilled water is added into the reaction liquid for extraction, and after the organic phase is dried, the pure product is obtained by utilizing column chromatography separation.

Step 6, preparation of phosphite ester

Adding the alcohol prepared by the reaction in the previous step into a reactor, and simultaneously adding a reaction solvent, wherein the reaction solvent is at least selected from triethylamine, ethanol, dimethylformamide, toluene, xylene, benzene, chlorobenzene, dichloromethane, carbon tetrachloride and ethyl acetate;

under the protection of nitrogen, controlling the reaction liquid at 0-20 ℃, dropwise adding phosphorus trichloride with the molar quantity of - of a third to a half of alcohol substances into the reaction liquid for 0.5-5 hours, heating the reaction liquid to 130-135 ℃ after dropwise adding and keeping the temperature to continuously reflect for 2-10 hours, and refluxing for 2-5 hours under negative pressure.

The reaction equation for phosphite preparation is:

in the reaction formula, n is an integer of 3-16.

And (3) monitoring the reaction process by using thin-layer chromatography, stopping the reaction when the color point of the reaction product in the fifth step is gradually reduced until the color point is not changed, improving the vacuum degree of a reaction system after the reaction is finished, uniformly evaporating a large amount of xylene and triethylamine from a three-neck flask, cooling, adding isobutanol for washing, further reducing the temperature of the reactant, crystallizing and separating the product, filtering, washing and drying to obtain the product.

Step 7, deprotection reaction of hydroxyl group

Adding the phosphite ester compound obtained in the step 6 and boron tribromide into a reactor according to the mol ratio

Phosphite ester: boron tribromide of 1:1 to 3

The boron tribromide used in the reaction is an ether solution of boron tribromide.

Simultaneously adding a reaction solvent, wherein the reaction solvent is at least selected from dichloromethane, chloroform and carbon tetrachloride.

And (3) adding the phosphite ester obtained in the reaction step into a three-neck flask containing dichloromethane, cooling the temperature of the reaction solution to 0-50 ℃, and slowly adding the dichloromethane solution dissolved with boron tribromide into the flask by using a dropping funnel, wherein the dropping time is 1-5 hours. And after the dropwise addition is finished, the reaction solution is returned to the room temperature and stirred for 2-5 hours.

The reaction equation for deprotection of hydroxyl groups is:

and (3) monitoring the reaction process by using thin-layer chromatography, and stopping the reaction when the color development point of the phosphite ester compound obtained by the reaction in the step 6 gradually becomes smaller until the color development point disappears. And transferring the reaction solution to a separating funnel, adding distilled water with the pH value of 7-8, repeatedly extracting, separating an organic layer, drying for 6-24 hours by using anhydrous magnesium sulfate, filtering to remove a drying agent, and evaporating the filtrate to dryness in vacuum to obtain a pure product.

The compound synthesized by the invention can be used as an antioxidant of polyolefin resin, and the compound is added into a polyolefin resin base material according to the mass percent of 0.01-1%.

The invention has the beneficial effects that:

the method is characterized in that a chemical synthesis method is utilized, two functional groups of hindered phenol and phosphite ester are simultaneously introduced into molecules, and the synergistic antioxidation of the two functional groups is increased while the due antioxidation effect of a single functional group is kept, in order to overcome the problem that a single functional group is small in steric hindrance and is easily separated out under the conditions of long-time placement, heat or solvent erosion as the molecular chain is loosely entangled with a polymer molecular chain after being added into polyolefin resin, a trimethylbenzene unit is introduced into the molecule, three hindered phenol structural units are simultaneously connected around benzene ring structures, the steric hindrance of the molecule is remarkably increased, the molecule is easily and stably entangled with the polymer chain of the resin, and the molecule is not easily separated out under the conditions of heat or solvent erosion, and meanwhile, the structure that trimethylbenzenes are simultaneously connected with three hindered phenol units is beneficial to improving the effective content of the hindered phenol units in the same molecule, and the antioxidation effect is further steps.

Nuclear magnetic description

Wherein n is a positive integer from 3 to 16;

1H NMR(500Hz,DMSO)，δ：9.01(s,9H),δ：7.15(s,18H),δ：4.56(s,6H)，δ：4.12(t，6H),δ：4.01(s，18H)，δ：3.47(t，6H)，δ：2.35(t，18H)，δ：1.39-1.58〔m，(6n-12)H〕δ：1.29(S，162H)。

in the nuclear magnetic spectrum of the compound, delta-9.01 represents a hindered phenol structure, and delta-4.56 represents-CH between a benzene ring and an oxygen atom₂-structure (i) (-) δ 4.12 represents-CH on a straight chain adjacent to the oxygen atom linked to the P atom₂-structure of (d) ═ 4.01 represents-CH between benzene ring and benzene ring₂Structure of- δ ═ 1.29 CH on tert-butyl₃-in the structure of (a).

Detailed Description

The following examples illustrate the invention in detail: the present example is carried out on the premise of the technical scheme of the present invention, and detailed embodiments and processes are given, but the scope of the present invention is not limited to the following examples, and the experimental methods without specific conditions noted in the following examples are generally performed according to conventional conditions.